Infections caused by or related to bacteria are a major cause of human illness worldwide. Unfortunately, the frequency of resistance to standard antibacterials has risen dramatically over the last decade, especially in relation to Staphylococcus aureus. For example, such resistant S. aureus includes MRSA, resistant to methicillin, vancomycin, linezolid and many other classes of antibiotics, or the newly discovered New Delhi metallo-beta-lactamase-1 (NDM-1) type resistance that has shown to afford bacterial resistant to most known antibacterials, including penicillins, cephalosporins, carbapenems, quinolones and fluoroquinolones, macrolides, etc. Hence, there exists an urgent, unmet, medical need for new agents acting against bacterial targets.
In recent years, inhibitors of FabI, a bacterial target involved in bacterial fatty acid synthesis, have been developed and many have been promising in regard to their potency and tolerability in humans, including a very promising FabI inhibitor, (E)-N-methyl-N-((3-methylbenzofuran-2-yl)methyl)-3-(7-oxo-5,6,7,8-tetrahydro-1,8-naphthyridin-3-yl)acrylamide. This compound, however, has been found to be difficult or impracticable to formulate into acceptable oral and parenteral (e.g., intravenous or subcutaneous) formulations, and has marked insolubility, poor solution stability, and oral bioavailability. Much effort, over a decade or more, has been expended to design and synthesize an alternative compound that retains the significant inhibition of FabI upon administration, but has improved physical and chemical characteristics that finally allow for practical oral and parenteral formulations. Up to now, no such compound has been identified that has adequate stability in the solid state, in aqueous solutions, together with excellent oral bioavailability that is necessary for oral and/or a parenteral administration, and is capable of being formulated into an oral and/or intravenous or intramuscular drug product using practical and commonly utilized methods of sterile formulation manufacture.